In some conventional liquid metering systems, such as, for example, those outputting, discharging, or dispensing hot melt adhesives or other thermoplastic materials, it is usually the practice to output or discharge a predetermined hot melt adhesive or other thermoplastic material by pumping such materials through a pump manifold, by means of, for example, a plurality of suitable metering pumps, to one or more outlets with which suitable output devices or applicators are operatively and fluidically connected so as to deposit the particular material onto a suitable substrate in accordance with any one of several predetermined patterns. Such conventional metering systems normally comprise a motor to drive the pumps at variable rates of speed in order to achieve the desired output volumes from the pumps in order to in fact achieve the desired depositions of the materials onto the substrates. Accordingly, the speed of the motor drive, and the resulting drive of the metering pumps, can be altered depending upon, for example, the speed of the substrate as the same passes by the output devices or applicators. Depending upon the structure or configuration of the particular substrate or product onto which the hot melt adhesive or other thermoplastic material is being deposited, it is desirable to be able to apply, output, or deposit more than one type of adhesive or thermoplastic material simultaneously onto a single substrate, that is, the system must be readily capable of processing multiple types of adhesives or other thermoplastic materials. While some systems can achieve the dispensing of multiple adhesives or other thermoplastic materials by supplying these adhesives or other thermoplastic materials to multiple applicators, or where the hot melt adhesives or other thermoplastic materials are being supplied by separate metering pumps into a common applicator manifold, the pressurization and spatial limitations of such systems have effectively prevented such systems from commercially achieving such outputted, discharged, or dispensed volumes of the hot melt adhesives or other thermoplastic materials as required or desired in a viable manner. For example, in order to supply the multiple types of hot melt adhesive or other thermoplastic materials to the adhesive manifold, multiple supply hoses must effectively be connected to the adhesive manifold for each separate, independent, or different hot melt adhesive or other thermoplastic material applicator which is in fact being supplied with the particular hot melt adhesive or other thermoplastic material, to be dispensed, from the adhesive manifold. Such a system becomes excessively bulky, burdensome, and complex.
A need therefore exists in the art for a new and improved hot melt adhesive or other thermoplastic material metering system which is readily capable of metering, for example, two separate, independent, and different hot melt adhesives or other thermoplastic materials from a single hot melt adhesive or other thermoplastic material manifold to a common output device or applicator such that the required application or deposition of, for example, the two separate, independent, and different hot melt adhesives or other thermoplastic materials onto a substrate or product can be achieved at predetermined times or locations, and in accordance with predeterminedly desired or required patterns, during a product processing run or operation.